Initial Commit

Most tests work (wrote some new ones as well)

Semantic Changes
Changed interface on PostFilters
items of app iterable are not compiled before sending
app can use both the write from start_response and returning an iterable

Technical Changes
Moved some of the replying into the StartResponse object, including calling
  PostFilters
All writes go through StartResponse.write
It tries to guess content-length
If no content-length, either chunks or closes the connection
All header checks go into StartResponse._finalize_headers
zmq socket.send uses NOBLOCK.  If our zmq buffer is filling, we have
  problems with our mongrel2 server. Just drop and log (this is also in
  preparation for gevent)
Handle exceptions in wsgi app better.
Merge branch 'steamraven/unbuffered-response' into develop
Fix log message